SEMINAR 11 [ ECO-FRIENDLY REFRIGERANT]

CHAPTER NO. 1

INTRODUCTION:-

Refrigeration is a process of maintaining the system at temperature below than the surroundings i.e. nothing but the heat removal from a space at a temperature lower than the surrounding temperature. This rushes the heat into the replace but insulation reduces the in-rush of heat. Whatever heat enters through the insulation into the refrigerated space has to be removed with the help of working media of refrigerator. These are called as refrigerants. Refrigerant is most important substance in the refrigeration. The present refrigerants used are chlorofluorocarbons (CFCs) and Hydrochloroflurocarbons (HCFCs)

Refrigeration applications at the domestic, commercial and industrial levels becoming an integral part of present day living. The demand of refrigeration is increasing day by day. So use of CFCs and HCFCs is increasing. But these refrigerants have a problem of ozone depleting potential (ODP) and global warming potential (GWP). Also it is very hazardous to human being. So it becomes very necessary to find the refrigerants which have no effect on the environments. These refrigerants have almost zero ozone depleting potential and negligible GWP. HCs, HFCs and natural fluids etc. are the well-known eco-friendly refrigerants. These refrigerants are described in detail below.

Necessity of Eco-friendly Refrigerants:-

Current refrigerants (CFCs and HCFCs) have two major drawbacks.

1. Ozone depletion.

2. Green house effect.

The stratospheric ozone (O₃) layer plays a beneficial role by absorbing most of the biological damaging ultraviolet sunlight called UV radiation, coming towards earth. Thus O₃ layer protects the human life food crops and natural eco-system.

But the leakages of CFCs are causing O₃ layer destruction and put a challenging problem before the scientists during the last two decades. CFCs, HCFCs contain reactive gaseous atoms of chlorine and bromine. Current levels of atmospheric chlorine are 3.5

parts per billion by volume (ppb) compare with naturally occurring levels of 0.7 ppb. These large chlorine levels are the product of the breakdown of CFCs in the upper atmosphere. These CFCs remain largely intact until they reach the stratosphere (15 to 50 km above earth’s surface) finally breakdown by UV radiations and releases chlorine. The released chlorine catalyses O₃ decomposition in the presence of UV rays

CCl₃F + UV à Cl + CCl₂F

Cl + O₃ à ClO + O₂

ClO + O à Cl + O₂

So that a long chain process in involved which conserves Cl atoms. Each Cl atom can destroy up to 1, 00,000 O₃ molecules before it washed out from the atmosphere. The destruction of O₃ is faster than its formation, therefore the net effect is reduction of O₃ layer or formation of O₃ hole like over Antarctica.

Second is the green house effect. Suppose this earth is the green house(where the vegetables are cultivated).The solar energy at short wave radiation enters inside earth surrounding atmosphere which contains CO₂ , CH₄ , N₂O etc. green house gases. These gases are transparent to short wave radiations. This short wave radiations when strikes the earth’s surface, converts into heat-long wave radiation. This long wave radiation is again reflected towards atmosphere but it cannot go out as the gases restricts the long wave radiations going out and traps the heat. This trapped heat contributes to the warming of earth’s surface. This is called green house effect.

This CFCs and HCFCs are also an opaque to the heat long wave radiations and thus increases temp. Of earth’s surface. And global warming takes place. The percentage of CFCs in atmosphere compared to CO₂ is negligible but its earth damaging effect is 100-1000 times more than CO₂.

This indicates that CFCs and HCFCs must be replaced within coming years throughout the world.

Table no. 1 Ozone depleting and Global warming potentials [1]

CHEMICAL	FORMULA		ODP	GWP	ESTIMATED ATMOSPHERIC LIFE (YRS)
CFCs
R-11	CCl₃F		1.00	1300	59
R-12	CCl₂F₂		0.93	3700	122
R-113	CCl₂FCClF₂		0.83	1900	98
R-114	CCl₂F₂CClF₂		0.71	6400	244
R-115	CClF₂CF₃		0.36	13800	539
HCFCs
F-22	CHClF₂		0.05	510	18
F123	CHCL₂CF₃		0.02	28	2
HFCs
F-134a	CF₃CH₂F		0	400	18
F-152a	CH₃CHF₂		0	46	2
OTHER REFRIGERANTS:-
Water-LiBr		7%H₂ox LiBr	0	0	-
Ammonia		NH3	0	0	-
Carbon dioxides		CO₂	0	1.0	230

Desirable properties of an ideal refrigerant:-

These are divided into four main groups:

1. Thermodynamic properties

2. Safe working properties

3. Physical properties

4. Other properties

1] Thermodynamic properties:

a] Boiling point:

Low boiling temperature at atmospheric pressure of the refrigerant is required for an efficient refrigerant. High boiling point of refrigerant at atmospheric pressure reduces the capacity of the system.

b] Freezing point:

Low freezing point of refrigerant is necessary because the refrigerant should not freeze under required evaporator temp. The refrigerant must have a freezing point well below the operating evaporator temp.

c] Evaporator and Condenser pressures:

It is always desirable to have positive pressures in evaporator and condenser for the required temp. but the pressure should not be too high above atmosphere. Too high pressures requires the robust construction of the refrigeration system which requires high initial cost and high operating cost also.

d] Critical temperature and pressures:

Critical temperature of vapour is defined as a temp above which the vapour cannot be condensed irrespective of any high pressure. The critical temp of the refrigerant used should be higher than the temperature occurring within the condenser for easy condensation of refrigerant vapour and critical pressure should not above the required condenser pressure of normally operated system.

e] Latent heat of refrigerant:

High latent heat of refrigerant at evaporator temperature is desirable because the refrigerating effect per kg of refrigerant will be high. Also high latent heat of refrigerant reduces weight of refrigerant required to be circulated in the system per ton of refrigeration and initial cost of refrigerant used in the system.

2] Safe working properties:

The safe properties of refrigerant include following:

a] It should be chemically inert.

b] It should be non-flammable non-toxic and non explosive both in pure state and when mixed with air in any proportion.

c] It should react with lubricating oil and with the materials used in construction of refrigeration system.

d] It should not have bad effect on the stored material when the leak develops in the system.

3] Physical properties:

a] Specific volume: Low specific volume of the refrigerant at the suction into the compressor is always desirable, because it reduces the size of the compressors for the refrigeration capacity.

b] Specific heat of liquid and vapour: Low specific heat of the refrigerant and high specific heat of vapour refrigerant are desirable because both tend to increase the refrigerating effect per kg of refrigerant. Low specific heat helps in increasing the sub-cooling of liquid and high specific heat of vapour helps in decreasing the superheating of vapour.

c] Viscosity: Low viscosities of refrigerants in both states are desirable for better heat transfer and low pumping power.

4] Other properties:

a] Odour: Odour may be an advantage or a disadvantage to a refrigerant. Distinct odour of the refrigerant helps in detecting the leaking of the refrigerant but it becomes irritating with an increase in concentration.

b] Leak tendency: The leakage of the refrigerant outside the system or leakage of the air inside the system is due to the opening the joist or flaws in material used for construction. A dense fluid has fewer tendencies to leak than lower density fluid. The possibility of leakage is more with high discharge pressure and low density refrigerant.

c] Refrigerant and oil relationship: The miscibility of the oil and refrigerant is an important characteristic in the selection of the refrigerant. The refrigerant should not act with lubricating oil as the refrigerant and lubricating oil will come in contact in compressor.

d] COP and power requirement: Low power consumption per ton of refrigeration is always desirable.

e] Cost and availability: The refrigerant must be available readily and with lesser price.

[1, 2]

CHAPTER NO. 2

MONTREAL PROTOCOL:

Looking into the danger of ozone depletion, in 1987, more than 150 countries have signed a protocol on curtailing the production and phasing out the CFCs on a global scale. India became a party to Montréal protocol in 1992. As per the protocol ODS (ozone depleting substances) like CFC-11, CFC12, CFC-113, CFC-115, HCFC-22, etc, will be phased out in developed countries by 2000 and in developing countries by 2010. HCFCs have considerably lower atmospheric life time and hence lower ODP.Asper the Montreal Protocol, HCFCs have also been included as controlled substances with virtual elimination by 2020 and total phase out by 2030. [1]

Montreal protocol and India’s commitment:

What one has been able to see particularly in the Montreal protocol is that suddenly some scientific fact is discovered which is realized to have a global community is called upon to share the responsibility of meeting this challenge forgetting for a moment as to who contributed nothing at all developing countries consumes ODS 0.3kg per capita per annum. India consumes far less than this. So the question naturally arose why countries, which consumes very little ODS should share in this global issue? But then India does realize its commitment to the global environment and hence accepted the principle of common and differential responsibility. India will get $82 million total as approved by the executive committee of the Montreal protocol. India’s CFCs production will not exceed 22588 tons this year 2003 and all of this will be phased out by 2010. [2]

Kyoto protocol:

Unfortunately Montreal protocol is bounded to only ODP, not for GWP so the substitutes HCFCs that are accepted as solutions for the Montreal protocol (ozone layer protection) are considered as contributing to global warming in the Kyoto Protocol came forward in dec.1997. Thus as far as Kyoto Protocol is concerned eco friendly refrigerants are the most important refrigerants which has zero ODP as well as GWP.[3]

CHAPTER NO. 3

Types of eco-friendly refrigerants:

a) Hydrocarbons

b) Hydroflurocarbons

c) Natural fluids

a) Hydrocarbon refrigerants:

Background:

Prior to the discovery of CFCs, HCs were widely used as refrigerants in domestic and commercial refrigerators. They were gradually replaced with CFCs due to its non-flammable nature.

But in the early 1990’s it was discovered that CFCs are very harmful and its major disadvantage is high GWP. So these were converted into HFC1134a and then into HC600a. Thus second conversion of CFC is very useful as it has higher energy efficiency and lower noise. The first HC compressors freely available in the market were HC600a compressors produced by Danfoos.

Advantages of HC-technology:

HC technology offers advantages on all three levels:

1. Global

2. National

3. Enterprise

Global level: The starting point (in 1990) for the development of HC technology was in

Germany and Europe. Many industries thought that only the most environment friendly technology HCs-should be used, since the HFC134a still has a factor of 1200 over CO₂emission sources. Thus it is a better ecological solution available as with HCs. Although Montreal protocol is bound to only the ozone protection, the HC advantages are well recognized in all bodies, the multilateral fund and they started to think globally.

National level:

In the past, this technology started with the ecological merits (no global warming) that help to make greens everywhere. This HC technology offers the chance to adopt national ‘natural’ solutions.

Enterprise level:

The most promising facts about HC technology are on the enterprise level. The technical advantages will be the main driving force to the HC technology. Today every industry is interested in the HC technology because of the other advantages with the production and daily use. These facts will be the future driving force for HC technology worldwide.

Technical advantages of HC technology:

1. No ozone depletion: - No ozone depleting effect is the prerequisite of all other (CFC) substitutes.

2. No global warming: - It is the starting point of HC movement.

3. No second conversion: - No second conversion such as the one hanging overall halogen compounds (e.g. HCF134a) is required in the long run.

4. Energy savings: - There is energy saving effect with an optimized refrigeration system of up to 10% over CFC and HFc134a.

5. Quite refrigerators: - The physical properties of isobutane (HC600a) refrigerators make for quiet refrigerators. It is an additional marketing aspect.

6. Readily availability: - The HCs cyclopentane-isobutane will probably be readily available most developing countries. They involve no synthetic chemistry, just purification.

7. New compressors self made:- For companies having own line of compressors manufacturing, it is a real chance for developing new compressors for

HC 600a and HC290 at least cost.

8. Extra ordinary reliability: With HC technology there are fewer compressors failures and no corrosion sooner or later because no chemical interaction between isobutene and mineral oil whereas CFC etc. leads to corrosion mostly due to moisture from high humidity. But HC compressors run forever (80000hours, 15 years) under standard test.

9. Virtually no refrigerants losses: Only disadvantage of HCs is their flammability. This requires careful design and thorough employee and service training. Due to danger of flammability, these substances are naturally handled with the almost care. This has the effect that there is virtually no refrigerant losses in the manufacturing process.

10. No-extra servicing equipment: It is another economical benefit. There is no extra servicing equipment necessary for isobutene over CFC whereas HFC134a requires completely new system additionally. HCs can be as safe as CFCs.

11. Technically simple to adopt: HC technology is simple to adopt in comparison to synthetic chemicals. Since the oils and compressors type are used, there is less strain and stress on management and work floor.[2]

HYDROCARBON REFRIGERANTS:

1. R600a: It is pure isobutene (also known by Care 10) and is primarily used in new domestic type equipment. It operates at significantly lower pressures than R12 or R134a, and hence its use requires modifications to components. it is not designed for existing R12 or R134a system.

2. R290/R600a: Care 30 is purified blend of propane (R290) and isobutene (R600a) with boiling point of -31.50 C at atmospheric pressure. The blend has been developed to produce a refrigerant with capacity to R12. Its major use will be in domestic refrigerators small commercial systemand transport refrigeration and air conditioning appliances. Though Care 30 has been formulated as replacement for R12, it can also be used in R134a system.

The advantages of Care 30 are

1. It has superior efficiency.

2. It has capacity similar to R12.

3. It is compatible with R12 system components including oil.

4. No system modifications are required that is no change of compressor, evaporator, condensers, thermostatic expansion value etc.

3 R290: It is pure propane (Also known care 40) and is primarily used in new equipments which would traditionally have used R22 or R502 systems, it may not give same performance as R22 or R502 and modifications may be required.

4 Care 50: It is an HC blend developed to replace R22 and R502 in existing installations with minimum modifications to the systems .It has boiling point of -49 degree Celsius at atmospheric pressure.

Effect of hydrocarbon refrigerants on the environment:-

Hydrocarbon refrigerants are natural substances with very short life-times-weeks and months rather than 100+ years for CFCs.Once in the atmosphere, they break down to CO₂ and H₂O. Although CO₂ is a green house gas (GHG), it is a very weak one. The significant effect of CO₂ on global warming is due to the very large quantities released through burning fossils fuel for power generation. The amount released by the use of HCs as refrigerants would be an extremely low proportion of the total. HC refrigerants contain no chlorine or bromine and, therefore, have no ODP. There GWP are related to the CO₂produced when they break down in the atmosphere and are comparing to other refrigerants.

Total equivalent warming impact:

The total equivalent warming impact (TEWI) is a measure of the total impact of a refrigerant in the system on global warming. Refrigeration can contribute twice to global warming.

· Directly through emission of those refrigerants which are GHGs.

· Indirectly through the use of energy generated by burning fossil fuels (which cause CO₂ emissions).

TEWI = direct effect + indirect effect

Table no. 2 Comparison of refrigerants on the basis of ODP and GWP [2]

Refrigerant	GWP (500 years basis)	ODP
R600a(care 10)	<4	0.00
Care 30	<4	0.00
R12	4500	1.00
R134a	420	0.00
R290(Care 40)	<3	0.00
Care 50	<3	0.00
R22	510	0.05
R502	4000	0.31
R404A	1400	0.00

Note: GWP relative to CO₂ =1 and ODP relative to R12=1

Refrigerant conversion: -

Hydrocarbon refrigerants have been known for decades, but have never been properly considered because of their flammability.

To determine the optimum HC refrigerant, trials were carried out in the context of the test series on the three relevant appliance groups: 1] Single temperature refrigerator; 2] Refrigerator with freezing compartment

3] Freezer (including no-frost).

The conclusions from tests were that, isobutane is the optimum refrigerant for all domestic refrigerators and freezers. The results in energy consumption and performance are the same or better when compared to R12 and R134a.

Through appropriate measures, such

1] Optimizing the foam system with cyclopantane,

2] Adding insulation thickness

3] Optimizing the cooling circuit components for R600a,

4] Using high efficiency compressors

We achieved with cyclopentane and isobutane refrigerators up to 10% lower energy consumption as compared with R11and R12 CFCs.Basically, R600a is a better alternative in the medium term, as it has very good thermodynamic properties and there is practically no direct contribution to the greenhouse effect.

From the safety point, it is clear that no-frost units can also be changed to R600a.Just in a short time after the introduction of the HFC refrigerant R134a, complete change of refrigerant is now eminent in the German and in the European domestic refrigerator sector as well.

This last change is gladly accepted, as technical problems with HCs are much more inferior to the ones faced with R134a. Therefore, where there has not yet been a conversion to R134a a changeover from R12 directly to R600a should be considered, without going through the difficult and costly route of R134a.

Liebherr (Refrigerator Company from Germany) was the first manufacture in the world to have phased out CFCs and HCFCs in its total production to cyclopentane /R600a, environment problems resulting from direct influence of the materials are solved.

Table no.3 Alternative refrigerants to CFC12 for domestic and commercial refrigeration appliances [2]

Parameter	CFC12	HFC134a	HC290/600a	HC600a
Formula	CF₂Cl₂	CH₂FCF₃	C₃H₈/C₄H₁₀	C₄H₁₀
Molecular weight	120.93	102.03	51.12	58.13
Critical temperature	112.0	101.1	96.0	135.0
Boiling Point (100kPa)0 c	-29.8	-26.16	-30	-11.73
Flammable Limits(%in air; 20degree c;100kPa)	None	None	1.8-9.0	1.4-8.4
ODP	1.0	0	0	0
GWP	3.1	0.26	<0.01	<0.01

Table no. 4 Comparative performance indices for leading refrigerant for domestic refrigerator [2]

Parameter	CFC12	HFC134a	HC290/600a	HC600a
Volume capacity(kJ/m3;-25 degree c)	1237	1185	1254	626
Pressure ratio (-25 0 c/55 0c) 32 0 c	11.03	14.07	11.42	13.39
COP theoretical	Equal to HFC134a	-	< or equal to HFC134a	More than HFC134a
Discharge temp. Theoretical	170-175	150-155	140-145	135-140

Evaluation of hydrocarbon technology:

Propane-isobutane mixture based appliances:-

The propane-isobutane mixture can be used with compressors designed using boiling temperature as guidance such that the design requirements of the freezer and the fresh food compartment in domestic refrigerators can be balanced. The normal boiling temperature for R290/R600a mixture (each 50% by mass) ranges from -32 degree c to -24 degree c, which is very close to normal boiling point of CFC12, the current refrigerant. The mixture, in comparison to CFC12, posses very high latent heat of vaporization and low value of density (one-third of CFC12), which makes the mixture attractive due to its low charge requirement and circulation rates. The charge levels are approximately 40% that of CFC12.One of the major advantages of R600a/290 blend is its compatibility with mineral oils and commonly used materials for manufacturing refrigeration system with minimum changes required in the refrigerant system.

The performance of these refrigerators as per BIS 1476 has been evaluated and compared with that of CFC12. However it was seen that with proper optimization of capillary length and amount of refrigerant charge, the performance level increases. There is almost no energy penalty the quantity of charge required is only 45g in comparison to 90g of CFC12. The mixture can be treated almost as a drop –in substitute. Refrigerators that are converted to propane-isobutane mixture are in normal operation for the past two years.

At present, a number of commercial refrigeration appliances, namely, visicoolers of various capacities and horizontal bottle coolers have also been converted to operate on propane –isobutane mixture. The performance of these appliances is also almost similar to CFC12 if length of capillary and amount of charge are optimized.

Isobutane-based appliances: -

Isobutane is a single component HC refrigerant with a normal boiling point of a -11.85 degree c. This refrigerant, in spite of having sub atmospheric pressure at suction, has been widely considered as one of the practical solutions for small capacities refrigeration appliances such as domestic refrigerator-freezer, deep freezer, chest freezer, water coolers.

In the first phase of the study, an isobutane compressor was designed and developed using the existing Indian compressors suited to 1 65-litre refrigerators. Subsequently, an Indian 165-litre refrigerator was modified to operate on isobutane refrigerant in April 1995. Then, the capillary length and amount of refrigerant charge were optimized to achieve energy efficiency. The performance of modified refrigerator was almost the same as that of CFC12. The performance of the compressor developed by domestic refrigerator manufacturers has been evaluated, the study of revealed that isobutane technology dose not require any change in the manufacturing process except for safety precautions. A similar approach has also been adopted for commercial refrigeration appliances.

Comparative study of isobutane (HC) and HFC134a technologies:-

Following table shows a comparative study of HFC134a and isobutane-propane and isobutane technologies from the point of view of manufacturing and servicing.

Table no. 5 Comparison of isobutene (HC) and HFC134a technology [2]

HFC134a	HC
Lower system efficiency. Deep change in compressor manufacturing processes. Highly sensitive to moisture content. High degree of cleanliness for the whole refrigeration system. Relatively higher noise level. Non-flammable. Higher cost of refrigerant and lubricant. No safety measures are required	Higher system efficiency. No change in compressor manufacturing process. Negligible sensitivity to moisture content. Low order of cleanliness is acceptable. Low noise level with isobutane as refrigerant. Flammable. Low cost Safety measures are required.

b) Hydro Fluorocarbon Refrigerants (HFC):

These HFCs are used as substitute’s refrigerants for CFCs such as R12, R22 etc. The detail description of HFCs is described below.

Design consideration:-

Suction pressure: - Suction pressure is almost similar for R12, R134a, and R290/600a Blend; it is much below the atmospheric pressure for R600a, particaly for low evaporative pressures. This makes the gas leakage on the suction side of the circuit more critical air ingress is possible, and system pollution is a consequence.

Discharge pressure:-

Discharge pressure is also similar for the three above-mentioned refrigerants, but it is approximately half for R600a. This will produce less stress and pulsations of the gas in the discharge side with the potentially lower noise.

Specific volumetric capacity:-

Specific volumetric capacity of RC600a is only half when compared to other alternative as consequences, keeping constant cooling power of the system; the displacement of the compressor must be increased.

Compressor manufacturers have been using all the design techniques to reduce this displacement increased as much as possible. Improved of the volumetric efficiency, reduction of gas temperature to increase it’s density at the suction etc. have been applied and in general the displacement increased have been limited top 70-80%.

Theoretical efficiency:-

The theoretical efficiency of R600a is higher than others and related impact on the GWP is smaller. The actual efficiency must be checked because the normal life cycle of a refrigerator is determined by continues alter Nance of the non steady situation and that is significantly different from the theory.

Working parameters:-

Working parameters of the R290/600a (50:50) blend are similar to R12 or R134a.

Table no. 6 Characteristics of potential substitute’s refrigerants (HFC) [2]

Refrigerant	Formula	Lower flammable limit(%volume)	Toxicity (ppm.vol.conc in air)	ODP (Relative to CFC11)	GWP(Relative to CO₂)
HFC123	CHF₃	Non-flammable	1000	0	--
HFC-32	CH₂F₂	74.6	--	--	--
HFC-125	CH₃CHF₂	NF	1000	0	2500
HFC-134	CHF₂	NF	--	0	--
HFC-134a	CF₃CH₂F	NF	1000	0	1200
HFC143a	CF₃CH₃	7.1	--	0	2900
HFC152a	CHF₂CH₃	3.7	1000	0	140

c) Natural Fluid Refrigerants:

AMMONIA:

Ammonia is a well known refrigerant used in large scale industrial application for more than 120 years. The know- how concerning the technology is widely dispersed in developed and developing countries. Never place it has not been used in air conditioning appliances or small refrigeration plants, despite the fact that Ammonia has excellent thermo dynamics and thermo physical properties, high efficiency in most temperature ranges, no ODP, no GWP, low refrigerant cost, great tolerance to water contamination.

Due to its strong smell, it is easily detected even at very low concentration.

The reasons for not considering Ammonia for the systems mentioned above are as given below:

· Toxicity at low concentration in air

· Flammability at high concentration in air

· No compatibility with Zinc or Copper or copper containing alloys high discharge temperatures.

The toxicity of Ammonia is usually not a major concern; the smell is noticed by a man at concentrations as small as 5 ppm. At the same time threshold limit value, which should not be exceeded for every day exposures is 50 ppm.

Ammonia is unbearable for human being at 5000 ppm, while its acute toxicity starts at 2500 ppm and the flammability at 15 vol. %.

Obviously any hazard announces itself far in advance making ammonia actually very safe refrigerant concerning direct hazards.

APPLICATIONS:

· Air conditioning-

In air conditioning of large buildings (centralized AC), Ammonia can be used as refrigerant as substitute for CFC11, HCFC123 and HFC134a.

· Supermarkets:

Presently, the use of Ammonia plants for cooling of medium and large super markets is increasing. This is due to introduction of secondary refrigerants (Brine) systems into the markets which has several advantages.

AIR: (729):

Air was one of the earliest refrigerants used. Air was used as primary refrigerant, and compression and d expansion of air took place without a change of state. Also it is readily available, non-toxic and nonflammable. But it is no used in large scale due to its high operating cost and low COP.

FEATURES OF AIR REFRIGERATION SYSTEM:

· It is simple, compact and has less weight.

· No separate compressor is required as a compressed air is readily available.

· It is easy to maintain and repair.

APPLICATIONS:

· It is widely used in air craft refrigeration system.

· It is also used in rail way air refrigeration system.

CARBON DIOXIDE (R744):

It is one of the most promising environment friendly refrigerants i.e. zero ODP and nearly zeros GWP. It has no toxicity and is also nonflammable. It is cheap and also no need for recovery. It is compatible with normal lubricants and construction materials. The main problem with this refrigerant is that it’s inherent high working pressure so due to this newly designed components redesigned.

APPLICATIONS:

· CO₂is used in commercial refrigeration system.

· It is also used in secondary refrigeration system.

· It is used in ship refrigeration system. [2]

Training needs for servicing of refrigeration appliances:-

Due to the substitution of refrigerants there is change in technology. And hence there is a problem of servicing occurred. So for that technologies of both refrigerants should be compared and the problem of training and servicing will be solved

à The issues of the service sector have to be addressed first before a major technology changeover takes place.

à There are thousands of mechanics who follow their own method of servicing. They need to be trained to adopt the changes.

à The market barriers for new technologies need to be identified.

à The manufacturers should come together for the same working proposition to recycle refrigerants to protect the environment.[2]

CHAPTER NO. 4

CONCLUSION AND FUTURE SCOPE:-

The thermodynamic, physical as well as safe working properties should be taken into account before selecting a refrigerant for a particular purpose. There is not a single best refrigerant which can be used for all refrigeration purposes. Different applications require different characteristics. But in view of the impact of refrigerant on ODP and GWP alternative i.e. eco friendly refrigerants are studied and properties are compared for the stability of existing system. And it is concluded that the refrigerant which causes ODP and GWP should be phased out as early as possible. And eco-friendly refrigerants should be used in all refrigeration systems.

Nowadays all foreign refrigerator companies like WHIRLPOOL, LG SAMSUNG including Indian companies like VIDEOCON, BPL, GODREJ are eager to produce CFC free refrigerators. Thus there is big future scope for the eco-friendly refrigerants.

REFERENCES:

1] ARORA and DOMKUDAVAR “A Course in Refrigeration and Air conditioning” Dhanpat Rai publication

2] “ECO-REFRIGERATION” a book published on “Conference on Hydrogen fluids and Commercial Refrigeration appliances.”

3] Iyer R. S. [Engineering Consultant (Ex. General Manager R and D, VoltaLtd.), Mumbai] “MONTREAL PROTOCOL AND KYOTO PROTOCOL” AC & R/23-25 august 2002/IIT Mumbai/1-6”

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